Brent North Sea crude hit $36.05 a barrel, the lowest level since May 2004.

West Texas Intermediate (WTI) dropped to $34.12 a barrel -- the lowest since February 2009.

Crude prices continued to slide as an ongoing supply glut showed no sign of easing. Figures released Friday showed a rise in the number of US rigs drilling, increasing worries that output will continue apace.

This added to "the already prevailing negative sentiments in the market due to the build-up in inventory", said Sanjeev Gupta, head of the Asia-Pacific Oil and gas practice at professional services organisation EY.

Gupta added that the lifting of the US export bans could negatively impact "long-term futures prices". US lawmakers last week lifted a 40-year ban on oil exports, a historic shift, even though analysts say the world supply glut is still the main driver of prices in the short term.

Prices have meanwhile slumped by almost one fifth since December 4 when the OPEC oil producers' group decided against limiting production, despite tepid demand and the supply glut. Oil has sunk more than 60 percent from above $100 in mid-2014.

Energy-rich Azerbaijan, whose economy has been hit hard by falling oil prices, withdrew support for its embattled currency on Monday and the manat plunged by nearly a third against the greenback. The manat was trading at 1.55 against the dollar on Monday, down 32.3 percent from Friday.

Around 1315 GMT, Brent North Sea crude for delivery in February stood at $36.24 a barrel -- down 64 cents compared with Friday's close.